refactor: reduce cognitive complexity of create and list operations

[kaladron]

No description provided.

[codspeed-hq]

Merging this PR will not alter performance

✅ 7 untouched benchmarks

---

_{Comparing kaladron:reduce-complexity (791ae26) with main (a997eda)}

[codecov]

Codecov Report

❌ Patch coverage is 90.90909% with 7 lines in your changes missing coverage. Please review.
✅ Project coverage is 96.84%. Comparing base (cef2373) to head (791ae26).
⚠️ Report is 5 commits behind head on main.

Files with missing lines	Patch %	Lines
src/uu/tar/src/operations/list.rs	88.63%	5 Missing ⚠️
src/uu/tar/src/operations/create.rs	93.93%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #303      +/-   ##
==========================================
+ Coverage   96.78%   96.84%   +0.06%     
==========================================
  Files           9       11       +2     
  Lines        1121     1492     +371     
  Branches       28       29       +1     
==========================================
+ Hits         1085     1445     +360     
- Misses         35       46      +11     
  Partials        1        1              

Flag	Coverage Δ
macos_latest	96.84% <90.90%> (+0.06%)	⬆️
ubuntu_latest	96.84% <90.90%> (+0.06%)	⬆️
windows_latest	0.00% <0.00%> (ø)

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[kaladron]

I'm factoring out some code to make it easier to follow. I've also sent #304 to make the coverage warning non-blocking since it's falsely failing here.